A shot in the dark: how vampire bats zero in on blood

Vampire bats have heat-sensing molecules that may help them strike at prey …

If you're working under the cover of night, it's probably not easy to pinpoint a tiny vein on an animal as big as a cow. However, this is a familiar scenario for vampire bats, which must spot a vein quickly and accurately if they're to get a meal. Now, scientists have figured out how vampire bats can identify where a victim's blood flows before it attacks. According to new research in Nature, this ability may be due to a novel mutation that helps bats sense heat.

The authors found that vampire bats have a unique version of a heat-sensing protein common to many other animals. Humans use this receptor, called TRPV1, to determine when an object or surface might be too hot to touch; our version of the receptor can sense when temperatures reach more than 43º Celsius (about 109º Fahrenheit).

However, researchers found that the unique TRPV1 isoform that vampire bats have, called TRPV1-S, is sensitive to temperatures over 30º Celsius (about 86º Fahrenheit). The "S" in TRPV1-S stands for short, since this isoform is 62 amino acids shorter than the more common version of TRPV1. While vampire bats express both versions of the receptor, no other animal is currently known to produce TRPV1-S.

Because this variant is not found even in very closely related species, it is likely an evolutionary solution to a unique problem faced by vampire bats: how to strike quickly and accurately enough to draw blood without panicking their prey. The more accurately a bat can strike, the better its chances of getting a meal. The extra sensitivity provided by the short variant may help these bats tune in to "hotspots" on their prey, where warm blood flows close to the skin's surface.

Beyond merely identifying this variant, the study also used TRPV1 to assess evolutionary relationships between species. Previously, bats were thought to be related to humans, lemurs, and rodents, but recent research suggests that they may be more closely related to cows, dogs, moles, and dolphins. By looking at TRPV1 gene organization, the researchers found that exon splicing in cows and dogs is very similar to that in bats, supporting the newer phylogenetic clustering.

Kate Shaw Yoshida / Kate is a science writer for Ars Technica. She recently earned a dual Ph.D. in Zoology and Ecology, Evolutionary Biology and Behavior from Michigan State University, studying the social behavior of wild spotted hyenas.